Field of the Invention
The present invention generally relates to a variable magnetization machine controller. More particularly, the present invention relates to a controller that is able to reduce the voltage induced by a pulse current to control a variable magnetization machine, such as an electric motor or other type of variable flux machine, that is employed in an electric or hybrid electric vehicle, at the reduced voltage.
Background Information
Electric vehicles and hybrid electric vehicles (HEV) include an electric motor that operates as a drive source for the vehicle. In a purely electric vehicle, the electric motor operates as the sole drive source. On the other hand, an HEV includes an electric motor and a conventional combustion engine that operate as the drive sources for the vehicle based on conditions as understood in the art.
Electric vehicles and HEVs can employ an electric motor having variable magnetization characteristics as understood in the art. For example, the magnetization level of the motor can be increased to increase the torque generated by the motor. Accordingly, when the driver attempts to accelerate the vehicle to, for example, pass another vehicle, the motor control system can change the magnetization level to increase the torque output of the motor and thus increase the vehicle speed.
In a typical motor control system, an inverter applies the control voltage to the motor. As understood in the art, as the current pulse width is shortened, the ramp rate of the current pulse, such as the D-axis current pulse, will increase. Naturally, this current pulse will affect the voltage induced in the control system.